Electromagnet structure



Sept. 23, 1947. A. wARsHER ELECTROMAGNET s'rrifiqzwnn Original Filed Sept. 25, 1940 Adel ab new/w Sept. 23, 1947. A. WARSHER ELECTROKAGNET STRUCTURE Original Filed Sept. 25; 1940 2 Sheets$heet 2 Patented Sept. 23, 1947 ELECTROMAGNET STItUCTURE Adolph Warsher, Maywood, N. J., assignor, by mesne assignments, to Maxwell M. Bilofsky,

Newark, N. J.

Original application September 25, 1940, Serial Divided and this application March 21, 1944, Serial No. 527,409

7 Claims. '(Cl. 175-21) The present invention, while shown applied to an electromagnetic relay of special utility in the starting and operation of thermionic lamps is or more general application to other constructions of electromagnets and relays for other purposes.

The invention constitutes an improvement upon that described and claimed in the prior Patent No. 2,159,837 granted to Duro Test Corporation on May 23, 1939, on application filed by Maynard A. Babb and SamuelJ. A. M. Bagno.

Among the objects of the invention are to provide a relay comprising readily stamped parts, easily assembled with a high degree of accuracy from a number of sub-assemblies each of which in turn is readily and accurately assembled.

Another object is to provide a magnetic yoke structure the relative sliding displacement of lateral separation of the laminations of which is precluded in the course of impregnation, adjustment and use, and assembly of which with the electromagnetic coil is easily effected, without the likelihood of tearing or scufllng the paper liner thereof or short circuiting or otherwise disturbing the predetermined fixed small air gap of the yoke structure.

Another object is to provide an electromagnet structure of the foregoing type, in which without the need for annealing and heat treating the magnetic parts to that end, release of the armature is promptly effected without delay due to magnetic retentivity-upon collapse of the magnetic field, and this without imposing an undue mechanical load upon the coilin effecting attraction of the armature.

-Another object is to provide a relay of the above type in which the effectiveness of contact operation is not impaired by any stresses evolved in the course of use as. for example those due to heat, that might cause among other disturbances the warping of heat insulating carrying parts, and in which contact is resiliently main-- tained closed with a minimum of contact resistance and is inherently released by the resilience of a contact carrying arm, in response to movement of the armature.

The present application concerned more especially with the electromagnet and yoke structure is a division of my present application, Ser. No. 358,190, filed Sept. 25, 1940, now Patent No. 2,351,377, granted June 13, 1944.

In the accompanying drawings in which is shown one of various possible embodiments of the several features of the invention,

Fig. 1 is a front elevation of the relay,

Fig. 2 is a sectional view taken on line 2-2 of Fig. 1,

Fig. 3 is a plan view thereof,

Fig. 4 is a dropped perspective of the portions of the yoke, showing the mode of assembling the same,

Fig. 5 is a perspective view of the armature and contact sub-assembly,

Fig. 6 is an exploded perspective view of the armature and contactsub-assembly,

Fig. 7 is a perspective view of the auxiliary yoke,

Fig. 8 is a transverse sectional view on line 8-8 of Fig. 7, and on a larger scale.

Fig. 9 is a perspective view on a larger scale of the armature holder bracket, and

Fig. 10 is a transverse sectional detail view taken on line 9-9 of Fig. 3.

Referring now to the drawings, the yoke is desirably made ,up of a stack ll! of E-shaped plates of suitable ferrous metal, each lamination including a beam ll lateral legs l2 and a median leg Hi. The stack is held together prior to impregnation by means of a single rivet l4 midway through the beam.

Coacting with the assembly of E-shaped laminations is a stack [5 of I-shaped laminations which has lateral keeper plates [6 of nonmagnetic metal, desirably of brass, between whichthe stack of I-laminations is sandwiched, the said members being held together by a rivet l'l midway therethrough,

The keeper plates are desirably provided with ears l8 at the lower edges thereof bent under the I-stack and serving thereby to prevent the laminations from pivotal or sliding relative displacement about the rivet IT. The keeper plates also have short lateral lugs l9 which in the assembled construction extend over the extreme laminations of the E-stack at the lateral legs thereof. Likewise the keeper plates have unitary therewith longer arms 20 protruding upward from midway between the ends thereof to have sandwiched therebetween the stack of laminated portions making up the median leg I3 of the E-stacks.

The electromagnetic coil 2i may be readily passed over the upstanding median arms 20 of the keeper plates, without the danger or likelihood of tearing or scuffing the paper liner 22 upon which the coil is usually wound. Thereupon, the E-stack may be readily assembled with respect to the coil and the I stack by passing the median leg [3 of the E-stack between the two upstanding arms 20 of the keeper pieces.

3 thereby pressing the arms 24 firmly against the coil liner 22. Thus the magnetic parts are kept out of contact with coil 2| by the interposed brass arms and all danger of short circuiting the air gap described below is obviated. The extremities of the keeper arms 20 may now be turned inward as at 23 thereby to maintain the two stacks of laminations securely assembled. Desirably the ends of the keeper arms 20 are bifurcated as at 24 near the top for facility of assembly, without interference from the'heads of the rivet l4 which is exposed between the arms of the bifurcations.

While the air gap of the magnet may be made in conventional manner, it is preferred for this purpose to follow the teachings of the prior application of John P. Glass, Serial No. 346,678, filed July 22, 1940. It may be briefly set forth that for this purpose, there is interposed between the contiguous faces of the lateral legs 12 of the E-stack and the ends of the I-stack, a metal rod or wire 25 that fixedly determines the size of the air gap and the ends of which may be hooked around the lateral lug 19 on the keeper plates l6, or if desired, they may be threaded through corresponding apertures (not shown) in said keeper lugs.

The assembly is vacuum impregnated with suitable synthetic resin varnish which is later baked to form a hard insulating coating on the outside of the yoke and coil structure.

The assembled yoke as described is a fixed, invariant unit which will sufifer no changes in its magnetic constants as a result of vacuum impregnation, installation or use, for the keeper plates 15 prevent at all times any rotary displacement of any of the laminations about the rivets or any lateral spreading of the laminations otherwise likely to occur particularly at their ends.

In the particular form of relay shown, an al1x ,iliary yoke 26 is passed through the electromagnetic coil prior to passing the latter over the keeper arms l6 and is disposed in snug engagement with one of said keeper arms 20, and thereby magnetically spaced from the laminated stack it). The auxiliary yoke 26 has a pair of poles 21 and 28 extending in parallel relation and straddling the coil 2!.

The armature 23 and the associated relay contacts 30 and 3i are desirably built as a subassembly to be affixed to the main yoke assembly. This sub-assembly in a preferred embodiment comprises an armature holder plate :32 of nonmagnetic sheet metal, desirably of brass, which has a transverse stepped slot therein. The widest portion 33 of the slot accommodates the entire width of the armature 29 for convenience of assembly. A contiguous slightly narrower portion 34 of the slot is of width to be straddled by lateral hinging notches 35 in the armature plate. The narrowest portion 36 of the slot defines shoulders 31 to be engaged by one face of the armature plate at the region between the hinging notches 35, the opposite face of the armature plate being engaged by the outer edge of the pole 21, when the holder plate is aflixed in place upon the pole 21 in manner to be set forth below.

Desirably, the armature holder plate 32 is in the form of a bracket which includes a unitary wing 38 extending generally lengthwise of the armature, with a tongue 39 at its extremity, which mounts an insulating fiber button 40 that serves as a limiting stop for the armature in its hinging movement on notches 35.

Riveted as at 4| to the armature holder plate is a fiber plate 42 upon which are. mounted the relay contacts 33 and 3|. 'Each of these contacts is at the end of a corresponding arm, 43 and 44 respectively, the width of which rises from the plate 42 and the length of which extends longitudinally of the plate, each of said arms having an outturned base lug 45 riveted as at 44 to the fiber plate. The arm 43 is desirably of substantial length, nearly that of the fiber plate and of phosphor bronze, spring-hard to have sufilcient resiliency to bias the contact 30 carried thereby away from the companion contact 3| to open circuit position.

The reduced extremity of the armature 23 at the hinge end thereof desirably carries a rod 41 of hard fiber extending from opposite faces of said armature. To mount said fiber rod the end of the armature is preferably bifurcated as at 44 to form fingers 49 which may be spread apart for insertion of the fiber rod therebetween and upon forcing the arms back to original position,

- the notches 50 therein will lodge in a corresponding peripheral groove Si in the rod for securely mounting the same.

4 Riveted to the wing 38 of the armature holder bracket is a spring steel plate 52, the end of which engages the corresponding extremity of fiber rod 41 and transmits thrust through the other end of the rod which engages the spring contact arm 43. The spring 52 which may' be of Swedish spring steel of .006 inch to .008 inch gauge exerts sufficient thrust through the rod 41 to overcome the resilience of contact spring 43 and when no current is passing through the relay to maintain the contacts in closed position. By varying the angle of wing 38, the pressure of spring 52 may be adjusted in accordance with requirements.

The sub-assembly of armature and contacts is afiixed upon the main assembly by a pair of machine screws 53 the heads of which are lodged in corresponding apertures 54 in the fiber plate, the shanks of which extend through corresponding small apertures 55 in the armature holder plate 32 and the points of which are threaded into corresponding apertures 56 in the pole 21. Slight enlargement of the screw apertures 54 and 55 permits minor lateral adjustment in the position of the sub-assembly, prior to tightening the screws into the pole 21 to assure correctness in the alignment of the armature 23 with respect to the poles 27 and 28.

When the sub-assembly oi armature and com tacts is thus installed upon the main yoke assem bly, the end of pole 21 contacts the under face of the armature 2i] and prevents displacement the hinged part of the latter toward the other- .wise open larger part 33 of the slot in the armature holder plate 32.

The hinge mount of the armature is thus especially simple and efilcient, in that it dispenses with pintle pins and it affords a non-magnetic hinge for the armature.

In operation, the free end of the armature 28 strikes the end of pole 28. To assure dependable operation, that pole is desirably made of double thickness of magnetic material for concentration of magnetic flux thereat to enhance its effectiveness. For this purpose, an extra layer 51 of magnetic stock may be spot welded to the leg or pole 28.

To prevent operation of the armature with the frequency of the alternating current, a split phase operation is provided by resort to a shading coll. This coil comprises a, fiat loop 59 of copper passed over a median tongue 60 formed by slittinB aid pole 28 as at 0! to accommodate the lateral walls of the shading coil. The latter is securely aillxed by indenting the same into the pole as at 52. Thus .the shading coil does not protrude to any considerable extent from the pole of the auxiliary yoke, and the length of the yoke need not be much greater than the height of coil 2|, so that the reluctance of the magnetic circuit through yoke 28 and armature 29 is kept low. Desirably, the tongue 60 protrudes slightly beyond the shading coil as at 63. and the lateral portions of the pole 28 terminate somewhat below the central portion to avoid engagement by the armature and to give the proper flux ratios of the split phases, thereby to provide a limited area of impact for the armature and to prevent undesirable vibrations of the armature. I

For further assurance of retraction of the armature upon collapse of the magnetic field, means is provided to overcome the residual magnetic attraction of the pole faces for the armature when the coil is tie-energized. To this end a non-magnetic plated coat is provided at the magnetic area where the armature strikes the pole. This plated area may be provided either on the pole or on the armature, but preferably on the latter. To this end, the plated region of the armature that strikes the pole must present a thickness of non-magnetic character and a striking surface area of sufflcient hardness to withstand the repeated impacts wlthout appreciable wear or deformation. This coating may be plated upon the armature according to any approved practice, desirably by electroplating. A desirable striking contact metal is hard chromium, but

since that metal has magnetic properties, it

would, if plated directly upon the ferrous metal of the armature lack complete effectiveness for quick release. Therefore, hard chromium is used I as the facing layer 64 and is plated upon a base plated layer 65 of non-magnetic metal, desirably of copper, which latter is too soft to withstand the impact. Desirably the non-magnetic layer 65 of copper by which the magnetic flux dissipation at the striking area is promoted, has a thickness in the order of .0025 inch, while the hard chromium facing 64 may have a thickness in the order of .0005 inch.

For ease and neatness of installation it is desirable to extend downward and outward from the middle portion of the keeper plates IS, a pair of supporting or carrying legs 66 for the unit. These legs may be bent out as unitary parts of said keepers extending between the ears l8 downward and outward, desirably at an angle of about 45 degrees, with horizontal diverging toes or feet 61 bifurcated as at 68. These feet may straddle annular grooves 69 in small rubber grommets 10 through which headed fastening screws H extend for mounting the unit in position, a washer ll transmitting the thrust from the screw head to the grommet. The mounting means set forth affords a secure foundation for the relay, which will transmit no mechanical noises of operation or residual lamination hum to the socket or other device to which the relay is attached.

The legs 66 also afford a convenient location for the small condenser 12 disposed under the magnetic yoke and desirablyheld in place against said yoke by a phosphor bronze band 13 threaded at its ends through corresponding slots 14 in said legs. The leads 15 from the ends of the condenser extend upward to the contact lugs 45 to be soldered to contact tabs 16 riveted to the under face of the fiber plate 42 at the respective regions at which the contact lugs are riveted in place.

The entire assembly may be installed in a socket or other casting which constitutes no part of the present invention, and is, therefore, not shown;

When no current traverses the apparatus, the spring 52 by pressure transmitted through button 41 maintains the armature 29 against stop 40 and over-powers the resilient contact carrying arm 43 to retain it in closed circuit position. In the 7 use in gaseous lighting circuits for instance, when the circuit is closed, the armature 29 is attracted to pole 28 by pivotal movement and the rod ll engaging spring 52 moves toward said spring and displaces it and moves away from the spring arm 43, which by virtue of its inherent bias moves the contact 30 to open circuit position, which open position is maintained as long as sumcient current is passing through the coil 2|, a condition maintained during the normal operation of the lamp. In the starting operation, the stop 40 not only limits the maximum opening movement of the armature, and therefore the maximum air gap between the armature and the poles of yoke 26, but it also cushions the vibratory action of the armature. The damped operation of armature as set forth results in improved action, in that blackening of the gaseous discharge lamps on their ends occurs only after a much larger number of starts than if an undamped armature mount were provided.

As soon as the magnetic flux through the yoke Ill-l5 collapses either due to disturbance in operation or opening of the circuit, the spring 52 by pressure upon rod 41 moves the armature away from the pole 28 and the thrust transmitted through said rod 41 urges the arm 43 to contact closing position. The prompt release action results from the fact that the non-magnetic copper plated layer 65 upon the armature avoids the magnetic retentivity which otherwise would delay release of the armature and re-closure of the relay contacts. The reduced area of contact between yoke and armature by reason of the foreshortening of the lateral parts of the pole 28 also I contributes to the prompt release of the armature.

The shading coil 59 is particularly effective by its split phase action to maintain the armature in contact with the pole during the reversals of flux in the normal alternating current operation, so that hum or chattering of the armature is avoided.

Thus the parts making up the relayare readily assembled as two sub-assemblies, the main yoke assembly and the armature and contact assembly, and the latter is readily mounted upon the former as set forth. The spring arm 43 need do no mechanical work other than to carry its con tact 30 to open circuit position when rod 41 recedes therefrom. The retraction of the armature from the yoke is effected by the pressure of spring 52 independently of the spring arm 43. Thus contact closure is reliably maintained with a low without departing from the scope of the claims, it

is intended that all matter contained in the above description or shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desireto secure by Letters Patent is:

1'. An electro-magnet of the character described comprising a magnetic yoke structure including a stack of angular laminations, each including a beam and a plurality of arms, a. stack 01' I-shaped laminations presenting in association with said angular stack a generally rectangular yoke frame, non-magnetic metal plates laterally superposed over the I-laminations, each including an arm superposed over one of the legs of the angular stack, and inturned at their extremities over the beam of said stack, and an electro-magnetic coil encircling that leg of the angular stack which is retained between said nonmagnetic arms.

2. In an electro-magnet of the character described a magnetic yoke structure including a stack of angular laminations each 1IC1l1d1l'lg a beam and a plurality of arms, a stack of I-shaped laminations presenting in association with said angular stack a generally rectangular yoke frame, non-magnetic metal plates laterally superposed over the I laminations and including lugs superposed over the ends of the several legs of the angular stack, and a rivet maintaining the I nonmagnetic plates and the interposed I-shaped laminations in assembled position.

3. An electro-magnet of the character de-' scribed, comprising a magnetic yoke structure including a, stack of E-shaped laminations each including a beam, lateral arms and a median arm, a stack of I-shaped laminations, presenting in association with said E stack a generally rectangular yoke frame, non-magnetic metal plates laterally superposed over the stack of I-laminations and including median arms superposed over the median legs of the E-lamination and inturned at their extremities over the beam of the E-laminations, and an electro-magnetic coil encircling said non-magnetic arms.

4. A magnetic yoke structure comprising a stack of E-laminations each including a beam, lateral legs and a median leg, a single rivet through said beam and a stack of associated I-laminations,

means determining a fixed air gap between the ends of the legs of the E-laminations and the I- laminations, a pair of non-magnetic plates between which the I-laminations are sandwiched, a single rivet bonding said plates and said I-laminations together, said plates having lateral lugs overlapping the extremities of the E-lamination stacks and having elongated median arms overlapping the length of the median leg of the E- laminations and inturned at their extremities over the beam of said E-laminations, and an electro-magnetic coil encircling said non-magnetic arms and the interposed median leg of the E stack.

5. A magnetic yoke structure comprising a stack of E-laminations, a single rivet connecting the same together, a stack of I-laminations, nonmagnetic metal keeper plates between which said I-laminations are sandwiched, and a single rivet through said I-laminations and keeper platu therefor, each oi said keeper Plates having lateral lugs overlapping the extremities of the legs of the E-stack, means maintaining a small air gap between the respective lamination stack, said keeper plates each having a unitary leg protruding obliquely downward and having outturned each a long median arm overlappin the entire lengths of the median legs of the E-stacks and protruding beyond the beam of said E-stack, an electro-magnetic coil superposed over said median arms of the keeper plates, the ends of the median arms of said keeper plates being turned inward over said beam.

7. A magnetic yoke structure comprising a stack of E-laminations, a rivet therethrough, a stack of I-laminations, a pair of non-magnetic plates between said I-laminations are sandwiched, a rivet through said I-laminations and the keeper plates thereof, said keeper plates having lateral lugs between which the ends of the respective arms of the E-laminations are sandwiched, said keeper plates having each along median arm overlapping the entire lengths of the median legs oi the E-stacks and protruding beyond the beam of said E-stack, an electromagnetic coil superposed over said median arms of the keeper plates the ends of the median arms of said keeper plates being turned inward over said beam, each of said keeper plates having a median down and outturned portion, the two said portions servin as a support for the unit, each of said keeper plates also havin lateral inturned portions extending under the magnetic yoke.

- .ADOLPH WARSHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,883,773 Erickson Oct. 18, 1932 1,998,810 Getchell Apr. 23, 1935 2,061,920 Pifiath Nov. 24, 1936 2,235,425 Franz Mar. 18, 1941 1,812,312 Ytterberg June so, 1931 1,821,813 Nickle Sept. 1, 1931 2,208,399 Slepian July 16, 1940 2,351,377 Warsher June 13, 1944 1,818,318 Goddard Aug. 11, 1931 2,199,909 Burton May 7, 1940 

